Aluminium is known for its corrosion resistance. Untreated aluminium applications like traffic signs and applications at sea are respected examples. Although aluminium is a relatively non noble material it protects itself via a passive oxide layer. Corrosion resistance of Aluminium is sensitive upon certain points in particular, these will be addressed in this blog.

To design aluminium without corrosion take the following aspects into account.

  • pH value of the environment
  • Nobility of Aluminium
  • Crevice corrosion
  • Composition of Aluminum
  • Black corrosion

pH value of the environment

Corrosion resistance of Aluminium is influenced strongly by the pH value of the environment

For normal use, like cleaning, use fluids in combinations with Aluminium with a pH neutral value (7) to prevent corrosion.

To prepare Aluminium for surface treatment you can use this to principle to clean the surface with specific sour fluids. The surface needs to be neutralized and rinsed adequately afterwards to prevent corrosion issues!

phdiagram

 

 

 

 

 

 

 

 

 

Nobility of Aluminium

To avoid corrosion problems with Aluminium nobility of the material needs to be taken into account. Aluminium is a relatively non noble material and will therefore sacrifice itself on behave of more noble metals in moister environment. This leads to galvanic corrosion.

This is a serious aspect using Aluminium products, specialy in combination with other metal parts. To prevent this type of corrosion block out fluids, use the right combinations of metals in the same nobility level or isolate the metals from each other.

nobility

 

 

 

 

 

 

 

 

 

Crevice corrosion
crevice

In a moister environment fluid will creep between narrow crevice due to capillary motion. To prevent crevice corrosion you have to avoid small crevices. Crevice corrosion occurs between crevices with a distance in between 0.2 mm to 0.5 mm. The solution for this matter is to increase crevice distance and reduce amount of contact surfaces. For example: a line contact is better than a surface contact.

With acid or salt fluids the potential for crevice corrosion increases.

 

Composition of Aluminum

Last but not least, the composition of the aluminum alloy influences corrosion resistance of Aluminium. If corrosion resistance is low you can surface threat this material in different ways. Take into account it needs more effort than with better corrosion resistance material.
Aluminium corrosion

 

 

 

 

 

 

If you take these mechanisms into account your design is robust against most common corrosion issues. In that case you take advantage of the natural corrosion resistance of Aluminium.

What was your biggest insight about corrosion issues so fare?

Let me know in the comment box below. This way, you’re helping me and others to design a world with optimal Aluminium use… Thanks in advance!